Synthesis of spiro[2H-indole-2,1′-1H-isoindole]-3,3′-diones,spiro[1H-isobenzofuran-1,2′-2H-indole]-3,3′-diones and spiro[benzofuran-2,1′-isobenzofuran]-3,3′-diones via transannular reactions of eight membered ring intermediates

An auto oxidation-rearrangement product 4 was isolated from a high dilution reaction of ninhydrin with 3,4,5-trimethoxyaniline in water. A general synthesis of this compound and its derivatives 4–6 was devised by oxidation of tetrahydroindeno1,2-b]indol-10-ones 1–3 with sodium periodate to give isoindolo2,1-a]-indole-6,11-diones 4–6 in good yield. Compounds 4–6 can be easily transformed into spiro1H-isobenzofuran-1,2′-2H-indole]-3,3′-diones 8–10 , spiro2H-indole-2,1′-1H-isoindole]-3,3′-diones 11–13 and isoindole1,2-a:2′,1′-b]pyrimidine-5,15-diones 15, 16 in high yields. Analogous reactions were performed on 3-amino-5a, 10a-dihydroxybenzob]indeno2,1-d]furan-10-one ( 17 ) to give a dibenzoxocintrione 18 , spiro-benzofuran-2,1′-isobenzofuran]-3,3′-dione 19 and an isoindol-1-one 20 .